The tangs will have a growth spurt and then it will slow down. They kind of grow with the tank in my experience. So big tank, they grow quick. Small tank they grow slow. Purple, yellow, tomini all small tangs and should be fine. Sail fin and hippo should be fine for a long time in a 5 ft. Yes you can make it work by having a more open aquascape and more swim space. Give them lots of open spaces in the rocks so they have there own territory. Tangs are very territorial and I find having lots of spaces for them helps reduce aggression. I wouldn't be putting the yellow in the sump though for 2-3 months. The longer you wait to introduce all your tangs the harder it will be to add more as they will get territorial, personal experience. Although you can reduce the aggressiveness when adding a new tang by either adding another rock structure for them or by re-arranging the rock scape. You can also leave them in an acclimation box for a few weeks to see if they finally get over the each other. I honestly think those 5 tangs will be fine. I have 9 in a 6 ft tank and they seem fine. One lives in the sump, and has stayed tiny compared to the others. I really want him in the main display but 2x powders just don't always work. I'm going to attempt again once I get my new tank setup and probably introduce a powder blue along with the powder black and brown to disperse the aggression. The blue hippo is the boss though! They are a entertaining and weird fish to say the least
Edit to add more context, I've had most my tangs for almost 4 years and youngest 2 years. They are probably one of my favourite fish. Oh and bonus, they are awesome cleanup crew! I have no snails or crabs in my tank believe it or not, the tangs do a great job